It is well known to provide shuttered electrical connectors. Typically, the connector includes an aperture for receiving a plug to establish electrical contact between conductors of the connector arranged in the aperture and conductors on the plug. The shutter is usually biased towards a closed position so that ingress of dust is avoided when the connector is not in use.
One well known type of shutter comprises a one piece plate which is spring biased and moves across the face of the aperture in a plane approximately normal to the direction of plug insertion. The shutter is arranged behind the face plate of the connector to retain it in position but has the disadvantage of imposing considerable size requirements on the connector as the connector housing must have sufficient room to accommodate the shutter when it moves away from the aperture to expose the aperture. One attempt to solve this problem has used a two part shutter in which one part slides over the other when the shutter is opened to reduce by half the room required to accommodate the shutter in its open position. Examples of the known prior art are shown in U.S. Pat. No. 4,624,516 and GB-A-2,260,035.
A more compact arrangement is disclosed in U.S. Pat. No. 4,666,225 assigned to Siecor Corporation. This document discloses a shutter which is folded into the plug receiving aperture of a socket as a plug is inserted. The shutter is biased to a normally closed position by a coil spring. The shutter is proved with a plurality of slots through which socket contacts protrude as the shutter is folded into the socket. This enables contacts on the plug to establish electrical contact with jack contacts which would otherwise be obstructed by the shutter.
We have appreciated that the design of U.S. Pat. No. 4,666,225 suffers from a fundamental fault. The spring arrangement required to balance the forces on a shutter of this type is such that at least the outer contacts in the socket are at risk of shorting out on the coil spring.